1. Field of the Invention
This invention relates to an information recording or reproducing apparatus for recording and/or reproducing information by the use of an optical recording medium capable of recording information thereon with the aid of light energy. The present invention covers an apparatus for effecting recording only or reproduction only and an apparatus for effecting both recording and reproduction.
2. Description of the Prior Art
Microfilms, video discs, digital audio discs, DRAW (direct read after write) systems, etc. are known as applications of an optical recording system. What has particularly been attracting attention in recent years is the application of optical recording systems to information file systems, namely, the DRAW system using an optical recording medium in which a laser light or the like is stopped down into a minute spot on the optical recording medium and a thin film of metal such as Te or Bi is evaporated to form pits in the optical recording medium.
A feature of the DRAW system is that recording and addition of recording are possible on the part of the user. Also, information recorded on an optical recording medium by pit formation is unerasable and cannot be repetitively recorded, it resists aging well and can be said to be best suited for long-time preservation.
On the other hand, recently, research and development of erasable, optical recording mediums including magneto-optical materials such as lower-oxidized-state tellurium, MnBi, GdTbFe, GdCO, GdFeCO, GdDyFe, GdTbFeCO, etc. have been announced. Erasable optical recording mediums have the merit of permitting repeated recording, while they have the disadvantages of being inferior in stability of the recorded information when preserved for a long period of time, that is, they do not resist aging well.
Accordingly, it is desirable to make the best use of the merits of the two types of optical recording mediums, that is, to use the unerasable optical recording mediums for an information file intended for long-time preservation and to use the erasable recording mediums for a short period of time or for temporary information files. An example of application of the information files for long-time preservation is the field in which conventional microfilm has been used, and an example of the application of the short-time or temporary information file are buffer memories or the like of printers, etc.
However, these optical recording mediums generally differ in recording sensitivity and thus, there is no example of apparatus in which recording and/or reproduction can be effected on optical recording mediums having different characteristics, and it has been impossible to effect information filing in the same apparatus by making the best use of the merits of optical recording mediums different in characteristic.